The present invention encompasses methods for preparing solid soap and detergent compositions. More specifically, fatty acid esters are saponified with an alkali metal hydroxide in a liquid reaction medium comprising an alkyl nitrile to provide alkali metal salt soaps of low moisture content. Soaps prepared in this manner are used to "dry" wet process soaps or synthetic detergent crutcher mixes to achieve an intermediate moisture level without the need for heat energy.
Traditional soap making processes are typically carried out using alkali metal bases, fatty acid esters, and water as the reaction medium. Heretofore, wet soap making processes have been energy intensive for at least two reasons. First, heat energy is required to initiate and sustain the saponification of the fatty acid esters by the aqueous solution of base. Second, the soaps are highly solvated by the water from the aqueous reaction medium. Accordingly, when preparing a granular, flaked or bar soap product, some water must be removed from the hydrated soap, and heat energy is used for this water removal step.
Likewise, in the preparation of solid detergent compositions comprising a synthetic detersive surfactant and optional detersive ingredients, the typical commercial process encompasses slurrying the detersive surfactant and other ingredients in an aqueous medium (crutcher mix) to provide homogeneity. The aqueous crutcher mix must then be dried, typically, spray-dried, to secure homogeneous detergent granules. Spray drying is also an energy intensive process.
From the foregoing, it will be readily appreciated that any means whereby the high water content of wet process soaps or aqueous crutcher mixes can be adjusted to some lower level without heat input would be advantageous. However, simply absorbing the water onto inert filler ingredients is not a desirable means for securing a lower moisture level, inasmuch as filler materials add nothing to the cleaning performance of the final compositions.
Soap, in a form having a low moisture content, or substantially dry, would be an excellent material for adjusting the moisture content of wet soaps or detergent crutcher mixes. However, low moisture content soaps prepared without an energy-intensive drying step have not been available heretofore.
The co-pending applications of Peterson, entitled SOAP MAKING, Ser. No. 731,183, filed Oct. 12, 1976, and HYDRATED SOAP MAKING, Ser. No. 731,163, filed Oct. 12, 1976, the disclosures of which are incorporated herein by reference, describe means for preparing substantially anhydrous and/or low moisture content soaps without the need for a heat drying step. Soaps prepared by the Peterson process are used in the present invention as the drying agent for wet process soaps and aqueous crutcher mixes.
The co-pending application of Peterson, entitled BASE REACTANT, Ser. No. 731,176, filed Oct. 12, 1976, discloses and claims a composition of matter which comprises an alkyl nitrile and an alkali metal hydroxide, as used in the Peterson soap making process.